1. Field of the Invention
The present invention relates to an improvement of a reciprocating piston type compressor with an oil separator for removing lubricating oil from high pressure refrigerant gas discharged from the compressor.
2. Description of the Related Art
A reciprocating type refrigerant compressor is generally used for supplying compressed refrigerant gas to a refrigerating circuit in an air conditioning system for an automobile. Such a compressor, in general, comprises a cylinder block including a plurality of parallel cylinder bores arranged around the longitudinal axis of the cylinder block, double-headed pistons which are slidable within the respective cylinder bores for reciprocation between the top dead center and the bottom dead center, and a drive mechanism for reciprocating the double-headed pistons. The drive mechanism includes a drive shaft which is supported for rotation by the cylinder block through a pair of radial bearings, and is operatively connected to a drive source, such as an automobile engine, and an inclined swash plate or cam plate mounted on the drive shaft. The inclined swash plate is engaged with the double-headed pistons through shoes mounted on the respective pistons, and is supported by a pair of thrust bearings.
A lubricating oil is used for lubrication of the moving elements, in particular, the radial and thrust bearings in the compressor. The lubricating oil collects in the swash plate chamber after it is distributed to the radial and thrust bearings. Then, the lubricating oil in the swash plate chamber is entrained by the low pressure refrigerant gas from the external refrigerating circuit during the compressing process so that the discharged high pressure refrigerant gas contains the lubricating oil in the form of a mist. The lubricating oil a mist in the high pressure refrigerant gas tends to attach to inner surfaces of the refrigerating circuit in the air conditioning system, which will decrease the heat exchange efficient of the refrigerating circuit if the lubricating oil is not removed from the refrigerant gas before it is supplied to the refrigerating circuit.
Accordingly, in a prior art compressor, an oil separator is provided, separately from the compressor in a high pressure pipe between the compressor and the refrigerating circuit, for removing the lubricating oil from the high pressure refrigerant gas discharged from the compressor before it is supplied to the refrigerating circuit. The removed oil is returned to the compressor through an oil return pipe. However, the oil return pipe tends to be blocked since the return pipe has a small inner diameter and a relatively long length due to the arrangement of the refrigerating circuit around the compressor.
Thus, a compressor which has an oil separator integrally formed therein has been developed. Such a compressor with an oil separator integrally formed therein includes an oil reservoir provided the rear housing which is connected to the rear end face of the cylinder block. However, the compressor encounters a problem in that provision of an oil sump or reservoir to accumulate a relatively large volume of the lubricating oil in the compressor results in an increase in the volume of the compressor because of the space for the oil reservoir in the compressor.
Further, a long term suspension of operation of the compressor makes the lubricating oil flow out from the oil reservoir into a central swash plate chamber through a passage for supplying the lubricating oil to the bearings. A reverse flow of the high pressure refrigerant gas occurs from the oil separator into the central swash plate chamber through the empty oil reservoir and passage when the compressor starts after a long term suspension of operation. A provision of valve mechanism for preventing the reverse flow will decrease the reliability of the compressor because of a possible failure of the valve mechanism.
Furthermore, within the central swash plate chamber, the low pressure refrigerant gas, which flows along the wall of the central swash plate chamber, tends to prevent the lubricating oil from reaching the bearing. The poor distribution of the lubricating oil inhibits the use of plain or slide bearings for the radial and thrust bearings instead of roller or ball bearings.